28 March 2017

"Iron" polymer

An implant made of ultra-high molecular weight polyethylene replaced bone tissue

NUST MISIS company blog, Geektimes

We have news – Russian scientists have successfully tested spongy bone implants based on ultra-high molecular weight polyethylene (UHMWPE): 100% of the implanted samples have successfully taken root. Researchers from NUST MISIS, with the help of colleagues from the Blokhin Russian Cancer Center and the State Plant of Medical Preparations, learned how to create high-precision imitations of the structure of bone tissue, which made it possible to provide complete replacement of a bone defect, initiate bone regeneration processes and preserve the functional capabilities of the limbs. An article with the results of the study was published in the journal Materials Science and Engineering (Maksimkin et al., Multilayer porous UHMWPE scaffolds for bone defects replacement).

A picture from an article in MSE – VM.

"In the course of new experiments, the research team was able to study the structural and mechanical characteristics of the obtained samples both in vitro and in vivo," Alevtina Chernikova, Rector of NUST MISIS, commented on the work of scientists. – Thanks to the close cooperation of our university, the leading cancer center of Russia and the State Plant of Medical Preparations, the breakthrough fundamental research of NUST MISIS scientists has received practical development. In particular, the results of in vivo experiments made it possible to determine the degree of porosity of the inner layer and the size of the pores at which a strong fixation occurs in the bone defect by ingrowing connective tissue into the implant."

No, it's not Hamlet. This is the project manager, Ph.D. Fedor Senatov with the same implants.

Partial replacement of bones destroyed due to cancer, injury or surgery remains an important medical problem. In Russia alone, more than 70 thousand operations are performed annually to restore the integrity of damaged bone tissue. There are hundreds of thousands of such operations in the world.

Bone tissue has a natural ability to regenerate, but in the case of large defects, it may not be sufficient to completely restore the bone. Therefore, today various types of implants are used to restore damaged bone tissue. The materials used to create bone implants must have a number of specific properties: be biologically compatible with the human or animal body, have high mechanical properties, provide complete replacement of a bone defect and initiate bone regeneration processes.

Implants made of ultra-high molecular weight polyethylene 

Ultrahigh molecular weight polyethylene is well suited to the described criteria. For example, if we talk about mechanical properties, then in terms of strength / own weight, UHMWPE products are superior to steel. Therefore, it was potentially very well suited for the manufacture of porous implants, the structure of which would most accurately mimic porous spongy bone tissue. However, the extremely high molecular weight of the polymer does not allow the use of traditional methods of creating a porous structure (usually they are created by foaming).

The problem was solved by applying the methods of solid-phase mixing, thermal pressing and washing in subcritical water. In such a cunning way, a team of Russian scientists for the first time in the world solved the problem of simulating the complex structure of spongy bone tissue by creating multilayer UHMWPE scaffolds with a solid outer and porous inner layer. (Scaffold is a term from tissue engineering, scaffold technologies are used to regenerate bone tissue).

"Our scaffold consists of two layers, firmly connected to each other," says the head of the work, researcher at the Research Center for Composite Materials of NUST MISIS, Ph.D. Fedor Senatov about the material. – The first layer is solid, it simulates the cortical bone to ensure mechanical strength. The inner layer has pores of a certain size, so it can be colonized by recipient cells to accelerate fusion with surrounding tissues and ensure a firm fixation of the implant in the defect zone."

Fedor Senatov with his team

According to the experimenters, the listed features of the obtained scaffolds based on UHMWPE open up great prospects for the creation of bioimplants in restorative medicine, which scientists have proved in a new series of experiments.

Portal "Eternal youth" http://vechnayamolodost.ru  28.03.2017

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